My guess is Saturn stays solo, except for rural and small areas, where being with BPG would be good and give the consumer more of a choice.
As for the next Aura, I figured Buick will get the Insignia clone and that leaves Saturn to get something more on the lines of a watered down version; something a sheep would enjoy. Since Opel is moving up market, a bit, Saturn may need to be watered down or cheapened up to hit the right demographic.
Lastly, first drive, Insignia:
http://www.motortrend.com/roadtests/...ons_specs.html